为什么下载的zip文件里面文件比服务器少

下载的zip文件跟服务器上的个数不一样啊
string a = "";
        HttpWebRequest myReq = null; HttpWebResponse HttpWResp = null;
        try
        {

            myReq = (HttpWebRequest)HttpWebRequest.Create("http://xxx.xxx.xxx.xx/Images/MomanCamera/background/MomanCamera_background_icons__1000001.zip");
            myReq.Timeout = 5000;
            HttpWResp = (HttpWebResponse)myReq.GetResponse();
            HttpStatusCode httpCode = HttpWResp.StatusCode;
            long fileSize = 0;
            if (httpCode == HttpStatusCode.OK)
            {
                Stream myStream = HttpWResp.GetResponseStream();
                fileSize = HttpWResp.ContentLength;
                byte[] b = new byte[fileSize];
                myStream.Read(b, 0, b.Length);

                if (b != null)
                {

                   FileStream fs;
                    FileInfo fi = new FileInfo(@"d:\1.zip");
                    fs = fi.OpenWrite();
                    fs.Write(b, 0, b.Length);
                    fs.Close();
                }


            }
              }
        catch (Exception ex)
        {

        }
        finally
        {
            if (myReq != null)
                myReq = null;
            if (HttpWResp != null)
            {
                HttpWResp.Close();
                HttpWResp = null;
            }
        } --------------------编程问答-------------------- 大神求解啊

补充：.NET技术 ,  ASP.NET